Myocardial perfusion and viability assessment is important for many reasons:
- to diagnose, locate and grade the severity of coronary artery disease
- to identify candidates who would benefit from re-vascularization
- to evaluate response of re-vascularization
It refers to a state in which there is wall dysfunction but the perfusion (resting and stress) is normal; see: stunned myocardium.
It refers to a state in which there is decreased perfusion on stress but normal perfusion during rest (seen as reversible perfusion defect). These patients will significantly benefit from treatment.
In this the myocardium shows decreased perfusion on both stress and resting phase (seen as fixed defect) but the myocytes are viable and will benefit from revascularization; see: hibernating myocardium.
In this there is absent perfusion on both stress and resting phase (seen as fixed defect) and the myocytes are not viable. There will be no benefit from revascularization; see: myocardial infarct.
- thallium-201 SPECT
- excessive radiation dose (c.f. 99mTc-MIBI)
- redistribution may occur
- single injection for stress and resting phase
- 99mTc-Sestamibi SPECT
- less radiation dose
- no redistribution
- separate injections for stress and resting phase
- FDG-PET (for viability)
- based on the fact that myocardium utilizes glucose for metabolism when under effect of ischemia (hence the ischemic myocardium will show greater uptake than normal cells)
- under normal circumstances, it utilizes fatty acids for energy
- non-viable myocardium will not show any uptake
- cardiac MR perfusion imaging
- no ionising radiation exposure
- dynamic imaging with gadolinium for perfusion
- delayed imaging for viability assessment
- computed tomography myocardial perfusion imaging
- single phase or dynamic perfusion imaging during stress +/- rest
- coronary arteries can be assessed at the same time